The present invention relates to a fluid compressor which is used in refrigeration cycle apparatus, for example, and which includes a compression mechanism unit of helical blade type and compresses a coolant gas as a gas to be compressed.
Recently, there have been proposed fluid compressors called also helical blade type compressors. In such a fluid compressor, a cylinder is arranged in a sealing case and a roller as a rotating member is eccentrically arranged in the cylinder to revolve around an axis of the cylinder.
A blade is fitted between a circumferential surface of the roller and an inner circumferential surface of the cylinder to define a plurality of compression chambers. A coolant gas for use in the refrigeration cycle, i.e., a fluid to be compressed, is sucked into one of the compression chambers at one end and transferred to another compression chamber at the other end successively while being gradually compressed.
With the above-mentioned type compressor, it is possible to eliminate a problem, e.g., a failure in sealing, that is encountered in conventional compressors of reciprocal and rotary types, to improve a sealing performance for more efficient compression with a relatively simple construction and to facilitate manufacture and assembly of of parts of the compressor.
Meanwhile, there are two types of compression mechanism units, one being a horizontal type in which the direction of compressing and transferring the gas is set to be horizontal and the other being a vertical type in which the direction of compressing and transferring the gas is set to be vertical.
For a compression mechanism unit of such horizontal type, a roller is arranged with its axis lying in the horizontal direction, and a thrust surface of the roller, i.e., a contact surface between the roller and a bearing, lies in the vertical direction.
An oil reservoir for storing lubricating oil is formed in an inner bottom portion of a sealing case, and the thrust surface of the roller is partly immersed in the lubricating oil within the oil reservoir. Accordingly, wherever a sucking portion for the compressed gas is positioned, no problems occur in supply of the oil to the thrust surface of the roller.
On the contrary, for a compression mechanism unit of the vertical type in which the direction of transferring the compressed gas is set to be vertical, a problem occurs in efficiency of oil supply to the thrust surface of the roller on the sucking side depending upon the position where the gas sucking portion is located.
If the gas sucking position is located in an upper portion of the roller, the lubricating oil supplied to the thrust surface at the top of the roller flows down instantly for the structural reason. This results in a difficulty in sufficiently supplying the lubricating oil to the thrust surface at all times and increases wear of the thrust surface.
During stoppage of the operation, the roller is axially moved down because of its dead load. Thus, a small gap is left between the top of the roller and the thrust surface on the upper side, i.e., on the sucking side, and a positive sealing surface cannot be realized.
At the start-up of the operation, therefore, the sucked gas leaks through the gap at the sealing surface and the compression efficiency is hence lowered.
Further, since the gas is delivered from a lower portion of the compression mechanism which is immersed in the lubricating oil within the oil reservoir, the gas is delivered into the lubricating oil, and a problem occurs if the oil reservoir of the lubricating oil is located on the gas delivering side.
For the above reason, the compression mechanism with the gas delivering side located in an upper portion has been proposed. Japanese Patent Laid-Open Publication No. HEI 4-58086 previously filed by the applicant discloses, as one example of such compression mechanisms, a fluid compressor with the gas delivering side located in an upper portion and the gas sucking side located in an upper portion.
In the above-cited Publication, however, a structure for supplying oil to the thrust surface is not described specifically.